253 BC

By place

Seleucid Empire

• The second Syrian War between the Seleucids and the Ptolemies ends. Antiochus II regains much of Anatolia from Ptolemy II, including the cities of Miletus and Ephesus, and also the Phoenician coast.
• The war is concluded with the marriage of Antiochus to Ptolemy II's daughter, Berenice Syra. Antiochus divorces his previous wife, Laodice, and transfers the succession to Berenice's children.
• In recapturing the city of Miletus, Antiochus II overthrows the tyrant of the city. In response, the citizens worship him as a god in thanksgiving leading to the addition of Theos to Antiochus II's name.

  Roman Republic

• A second Roman war fleet of 150 ships is wrecked on the voyage from Lilybaeum to Rome.
• Tiberius Coruncanius is the first plebeian to be elected pontifex maximus of Rome.

  Greece

• Alexander, Antigonus II's nephew and regent, leads a revolt in Corinth with Ptolemy II's help and declares himself an independent monarch. As a result, Antigonus loses Corinth and Chalcis, the two bases from which he has dominated southern Greece. As the Aetolians occupy Thermopylae, Antigonus II is cut off from Athens and the Peloponnese.
• Macedonia's involvement in the second Syrian War ceases when Antigonus becomes preoccupied with the rebellion of Corinth and Chalcis, as well as an increase in enemy activity along Macedon's northern frontier.